1. Field of the Invention
This invention relates to hard disk drives and more particularly relates to hard disk drive redundancy.
2. Description of the Related Art
Data storage systems are storing increasing quantities of data for both organizations and individuals. Much information is stored in databases. In addition, the cost of storing information digitally is often significantly lower than storing paper copies. As a result, vast amounts of valuable information are stored digitally.
Because of the high value of digital information, it is important that digitally stored information is protected from loss. Data storage systems often store data redundantly to protect against loss. For example, a hard disk drive may employ error correction codes (ECC) to redundantly store data. The ECC may be used to recover lost data in a sector due to write errors, faulty media, and the like.
Unfortunately, if there are too many errors, the ECC is unable to recover the data. As a result, a data storage system may store data redundantly across a plurality of hard disk drives. For example, a data storage system may employ Redundant Arrays of Independent Disks (RAID) systems to store data redundantly.
In a RAID system, if a hard disk drive fails, the data of the hard disk drive may still be recovered from other drives in the system. RAID systems using RAID level 3, 4, and 5 redundancy utilize row parity between hard disk drives. RAID level 6 supports row and diagonal parity between hard disk drives.
However, these RAID redundancy schemes are still exposed to individual sector failures, which can kill an entire data stripe during the reconstruction of a failed drive. In addition, individual hard disk drives would be more reliable if the drives supported greater redundancy.